"A is A" does occur in Leibniz, who, among his many endeavors, worked on fashioning a symbolic form of Aristotelian logic. I haven't found "A is A" in anyone earlier, so I have suspected Leibniz for a while. But neither had I found anything scholarly that asserted his authorship of the formula.
Some years ago, Thomas Stone had sent me a note saying that Leonard Peikoff, in his lecture series on the History of Philosophy, had credited Antonius Andreas, a 12th century philosopher, with the formulation of the law of identity - of which "A is A" is a symbolic statement.
Today I found a document in French which states that Wilhelm Wundt, the famous German psychologist, specifically credited Leibniz with "A is A". This same French document mentions Antonius Andreas, but ascribes to him only a verbal form of the law of identity.
I have only a smattering of French - so I relied on the Google Translation, and fixed a few small things that even I was able to correct:
“The identity principle: Wundt says that “the law of identity was expressed for the first time in a pure logical form by Leibniz (Logik, T. II, p. 562)”. In fact, this one in proposed a great number of formulas, among which: “Each thing is what it is”, “A is A, B is B” (New Essays on Human Understanding, IV, 2, ed. Gehrardt, p. 343, sq.)… However Suarez already allotted to Antonius Andreas the following formula: Omne ens est ens, that it rejects besides like useless (Metaph., Disp., sect. III, n° 4)."
If this is correct, Leibniz gets credit for "A is A" - since it shows up in his New Essays on Human Understanding. Antonius Andreas gets credit for "Omne ens est ens." (Which I've seen translated as "Every being is a being." ) Aristotle, it is true, had already touched on the issue that a thing is itself. (Metaphysics Book VII, Part 17)
The French source is here, which seems to be a site for Thomist philosophy:
The Suarez referred to is Francisco Suarez, and his book in which he discusses Antonius Andreas is his Metaphysical Disputations.
My next step is to track down the work of Wundt that was cited, his Logik. There's a copy of it in a library in Chicago, but it's in German, another language I don't know!
If anyone can further correct the French translation, I will thank you. I also have this snippet of Latin in which Suarez speaks of Antonius' contribution:
"Prima sententia est non esse primum illud quod ex Aristotele retulimus, sed hoc, omne ens est ens. Ita tenet Antonius Andreas, IV Metaph., q. 5. Et ad Aristotelem respondet vocasse illud aliud primum principium inter ea quae circumferuntur ut generalia, ut sunt illa: Omne totum est maius sua parte, etc. Sed hic auctor etiam in suis principiis non recte loquitur, quia illa propositio est identica et nugatoria; et ideo in nulla scientia sumitur ut principium demonstrationis, sed est extra omnem artem."
If anyone feels up to translating that, I will be ecstatic. Corrections or pointers of any kind are welcome.
I'm putting this in Epistemology because, outside of Objectivism, "A is A" usually comes up in logic discussions. Really this is more of a History of Philosophy question, but there doesn't seem to be a category for that.
Edited by jenright, 05 December 2006 - 07:50 PM.